Unknown assailants broke windows and placed swastikas at the entrance to a Chicago synagogue overnight Friday-Saturday, in what local authorities said was a suspected hate crime.

The president of Loop Synagogue, Lee Zoldan, told NBC Chicago that the attack was witnessed by nearby construction workers.

According to Zoldan, the workers said that the incident began when a black SUV stopped outside the building a little after midnight, and one of the passengers got out and broke the windows using what appeared to be a hammer or an axe. The person returned to the SUV to collect the swastika stickers that were then placed on the front door.

Zoldan told NBC that Shabbat worship at the synagogue went ahead as planned.

The synagogue had not received any further threats, she said, adding that the board would consider increased security measures.

Swastika stickers were placed on the door of the Loop Synagogue in Chicago on February 4, 2017, in what local police said was a hate crime. (screen capture: NBC Chicago)

Swastika stickers were placed on the door of the Loop Synagogue in Chicago on February 4, 2017, in what local police said was a hate crime. (screen capture: NBC Chicago)

The Chicago branch of the American Jewish Committee condemned the attack and vowed that such actions would not scare the local community.

“The Chicago Jewish community will not be intimidated by anti-Semitic attacks on a house of worship,” AJC Chicago Director Amy Stoken said in a statement.

“The right of all religious groups to practice their faith without fear is a fundamental American value. Chicagoans must speak together clearly that the hatred behind this destructive behavior will never be accepted.”